Earlier quoted context omitted.
Energy efficiency is interesting, but it is important to see the whole picture. Maybe we should be using a land efficiency rating instead? Take reindeer meat as an extreme case. Their energy efficiency from converting lichens to meat is not going to be 100%, but the alternative use for artic land are quite few. Applying the same line of thought, we can find examples also for beef. There are cattle farms here in Swede…
With reindeers it is probably highly dependent on region. For example in Lapland of Finland there are way too many reindeers than the environment can support, so they are largely kept in pens during winter and fed protein feed, hay, collected lichen, dried feafy branches etc. Plus Finland produces about 2 million kilos of reindeer meat per year, so it is really miniscule part of the diet.
I do know personally a farmer that operated highland cattle in a nature protected forest. They do need hay during the winter months, but that is about it. For the rest of the year it is water, salt/minerals, and some shelter in case of really bad weather like large thunderstorms. The benefit for the forest is significant and directly noticeable, and looks like a really very well managed open forest. In contrast spruce forests which is the norm in the south part of Sweden tend to be extremely overgrown, which is currently recognize as an major threat to bio diversity. Several species has gone almost extinct because of it. There are a few other nature reservation that also use highland cattle with similar setup.
Technically highland cattle could survive the winter months without hay but it would not be legal.